Hydraulic governor head with speeder spring adjusting means



Apnl l, 1952 U E. J. COLLINS 2,590,940

HYDRAULIC GOVERNOR HEAD WITH SPEEDER SPRING ADJUSTING MEANS Filed Sept. 29, 1945 4 Sheets-Sheet 1 J07 .106 J5 4 filfizn.

fdward 60/117765. .9-

April I; 1952 E. J. COLLINS 2,590,940

HYDRAULIC GOVERNOR HEAD WITH SPEEDER SPRING ADJUSTING MEANS Filed Sept. 29, 1945 4 Sheets-Sheet 2 1/6 11 64 6 L03: 60 l l 13.] I A H W jttojway- April 1952 E. J. COLLINS 2,590,940

- HYDRAULIC GOVERNOR HEAD WITH SPEEDER SPRING ADJUSTING MEANS Filed Sept. 29, 1945 4 sheets-sheet a d I 4122 12,2 V138 Z I271/e/7Zan-- ward] all/1w. JOJ i] A rug/y.

E. J. COLLINS HYDRAULIC GOVERNOR HEAD WITH SPEEDER April I, 1952 SPRING ADJUSTING MEANS Filed Sept. 29, 1945 4 Sheets-Sheet 4 Co e/P Pit (quiz-02 Pazze IIICIEd Je IF. RM L97 4 LU J a J m M J m d 6 ia/ 17g Patented Apr. 1, 1952 UNITED STATES PATENT OFFICE HYDRAULIC GOVERNOR HEAD WITH SPEEDER SPRING ADJUSTING MEANS Edward J. Collins, Los Angeles, Calif., assignor to Raymond T. Moloney, Chicago, Ill.

Application September 29, 1945, Serial No. 619,382

means or head which is more reliable under severe flight conditions; which is of simple, rugged, compact and light-weight construction; which is readily adaptable to standard propeller installations and practices; which uses the engineoil at engine pressures as the hydraulic actuating medium for varying tension on the speeder spring;

which employs a novel, simplified solenoid valve means electrically controlled from the cockpit for selectively regulating the flow'of engineoil .rela-,

2 engine line ahead of the governor for use in the novel control unit or head; which provides a novel hydraulic locking means as part of the hydraulic tensi'oning means for the speeder spring so that any setting of the latter will be positively maintained, so far as the control exercised by the I governor head is concerned; and which afiords 'a device having the foregoing objects and advantages and which is at the same time less costly to craft for changing the pitch'of the propeller make and maintain than electric governor conblades while in flight, or operation. olsi In'ac'cordance with present practices on so- Additional objects; advantages, and aspects of called standard propellers, built-in piston and novelty of the invention relate to details of concylinder means in the propeller hub are actuated ,Strlletion and Operation of the l u ative emhydraulica'lly, under control of a self-contained d nt described in view of the annexed engine driven governor including a pilot valve gs in which:

for controlling oil now to and from the hydraulic F 1 s a p rsp tiv v w f a pr p l r vmeans, for the purpose of altering the pitch of ernor "head and the novel solenoid operated con- ,the propeller blades. tro1 head mounted thereon;

Said pilot valve in the governor, in turn, is o e- 2 is a op p n vi w, t l r l f controlled by a fly-weight type of governor balt device of anced by a single sprin known a a peeder Fig. 3 is a vertical section through the conspring; by changing the tension of this speeder d d pa f the governor head, taken spring the pilot valve is actuated variously to 'a1011g1ineS33 0f effect the pitch-changing function of the gov- Fig. 4 is a horizontal section, taken along lines ernor. 4-4 of'Fig. 3;

Various means have been employed heretofore Fig. 5 iS a hOIiZOIltEll SECtlOl'l, taken along lines for enabling the pilot to control the tension of the speederspring remotely from the cockpit, it being i 6 s fragmentary vertical section through understood that these governors are mlountedimone of the Solenoid Valve u its, taken in the dimediately behind the propeller; these prior con- 186111011 0f 1ineS of tro1 arrangements have included cable-actuated 1S a fragmentary t cal section lookrack and gear means as well as electric motor mg e direction of lines f means in various modifications, all of which are e 8 i elevation of e -line adapter;

subject to serious objections particuarly in highl 9 1S a clreuli? diagram;

. altitude operation, and all of which are relatively 5 is a Vertlcal Seetienel il through more bulky or complex or both than the gover the Switch housing showing the switches. nor h'eadof the present invention A complete governor head assembly is shown I The more detailed objects of the present invenm and l e a known ype f govertion include the provision of a governor control 4 nor umt, generally mdlcated at In, ed'by the novel control head generally indicated at H;

this assembly is mounted on the engine 'immedi- A ately behind the propeller, the governor unit including a base flange l2 provided with bolt holes I3 for this purpose.

While the invention herein disclosed and claimed relates to the control head, and only pertinent parts of the governor, such as the speeder spring are shown in detail, the description is facilitated by pointing out that the governor, includes a gear type of pump (not shown) driven from the engine by either a coupling .gear, splined shaft, or the like, situated within the governor head base portion l2; and it is the function of this gear pump to boost the pressure of themgine oil for the purpose of actuating the hydraulic pitch-changing means in the propeller hub, such actuation being under control of a pilot valve (not shown) in the governor head, which is in turn control1ed.by the speeder spring assembly.

The governor head I is provided at its upper end with a seating flange l4 onto which fits the base portion l5 of the control head body casting, the latter being secured thusly by nuts I6 on bolt studs H from said body casting.

In Fig. 3, only the uppermost portion of the governor head,.and particularly the flange I4 thereof, appears, but it is in this part of the governor that the speeder spring I8 is situated, the bottom part of the spring being seated in a presser disc H on a rod reciprocable to actuate the pilot valve (not seen) Presser disc l9 includes an annular riding portion 2| against which bear the offset lever arms 22 of fiy-weights 23, pivoted at 24 on fly-wheel 25 concentric with rod 20 and driven with the pump gear.

From the foregoing description of the speeder spring assembly, it will appear that the fiy- Weights 23, rotating with fiy-wheel 25, are thrust centrifugally outward, causing lever arms 22 to exert an upward lifting effort on the presser disc l9, which is counteracted to varying degree by the speeder spring l8 depending upon the tensioning of the latter under selective control of the pilot or engineer; and it will further appear that once the tension of the speeder spring is set, the control or actuating rod 20 for the pilot valve will be maintained in a certain position, which in efiect will correspond to setting and maintenance of the propeller blades at the desired pitch, and

rotation of the propellers at the required number latter, to selectively tension the said speeder spring by electrically controlled, hydraulically powered means utilizing oil from the engine, and at engine pressures for the purpose, as will now appear.

7 Referring to Fig. 3, the control head i I consists of a body casting having a large chamber in the base part I5 to enclose the speeder spring assembly, which, as heretofore explained, is part of the governor means, there being an extensive vertical piston chamber 3| above said chamber housingcertain hydraulic means for tensioning the-speeder spring, said hydraulic means including a piston rod 32 having a cup washer 33 screwed into its lower end and in which the upper, reduced, end of the speeder spring I8 is seated.

, Piston rod 32 extends upwardly through a sealing ring 34 in a lower cylinder sealing plate 'or disc 35 provided with a sealing ring 36 about its a groove in the cylinder chamber on the lower side of this disc whereby the latter is also held against downward displacement, so that in effect the disc 35 sealingly closes off the bottom of the piston chamber of cylinder 3|.

Higher up in the main cylinder is another seal ing plate or disc 40 stopped upwardly against a shoulder 4|, and downwardly against a stop gasket 42, there being an outer sealing ring 43 for the plate and a small inner sealing ring 44 about piston rod 32, so that in effect the main cylinder chamber is divided intoupper and lower subchambers or cylinders sealed off from each other, the upper sub-cylinder portions being indicated at A, A, and the lower portions at B, B.

In sub-cylinder B-B' is a control piston fast on rod 32 against shoulder 5| as held by sprung washer 52, sealing rings 53, 54 preventing passage of liquid around this piston.

Movement of control piston 58 downwardly compresses the speeder spring; movement upwardly relaxes said spring.

In the upper sub-cylinder A-A is a regulating piston 60 fast on rod 32 against shoulder 6| thereon as held by a sprung washer 62, sealing rings 64 and 65 preventing passage of liquid around this piston from chamber portion A to A and vice versa, movement of said liquid, however, occurring through a vent 66 from one face of this regulating piston to the other, chamber portions A and A being filled with a liquid having a viscosity affected as little as possible by temperature changes, and the diameter of the vent passage being selected for a liquid of given viscosity to regulate the speed of upward and downward displacement of the entire piston assembly to a desired average rate between the extremes of temperature encountered in aircraft operation, as otherwise there is an excessive difference in the speed of operation of the device at 160 F. as compared with the response at minus 65 F. for example, if such regulating means is not provided. A filling vent with closure screw 6'! is provided at the top of sub-cylinder A for introducing the special viscosity liquid into the regulating piston section.

As seen in Figs. 1 and 3, a cylindrical switch housing I0 is mounted on top of the control head by means of screws H in hold-down cleats 12 engaged in groove 13 on the housing.

Interiorly of the switch housing 10, Fig. 10, are a pair of adjusting screws 15 each having reduced studs 16 rotatably seated in the top of the head casting, the upper ends of these screws being flanged as at 17 with their slotted heads 18 projecting freely through the top of the casing 10.

Threaded onto each of the screws 15 is a switchsupporting bracket 19 having a curved side conformable to the inner curvature of the housing 10 such that the brackets may move up and down, but are prevented by interfitting curved portions at from swinging about their respective adjusting screws 15.

Carried on each bracket 19 is a sensitive switch, one of these being the upper limit switch 8|, and the other being the lower limit switch 82, and each said switch has an operating button, 83 and'83, the former being pitched oppositely from the latter for engagement by an operating washer 84 carried on the upper extremity of the piston rod 32; thus, when the piston rod moves toward its upper limit of travel, the rounded edge of washer 84 will cam button 83 inwardly to operate switch 8! in a manner to be explained; and when the piston rod moves toward its lower limit of travel, washer 84 will cam button 83' inwardly and operate the corresponding switch 82. The positions of said limit switches 8| and 82 are eiscoreeo I 5-- :determinedzbyrotatingthecorresponding"adjust in'g" screws 15' to raise or lower the: same; set screws 85' then being tightened against" the' stud portions 16' to secure the switches" in adjusted position; An elevation of the switch 81 is seen inFig; 3'. p

The hydraulic medium for operation of the control piston 50 is oil taken from" the aircraft engine and" utilized atengine'pressuresranging at fairly constant values between 38' and 50 pounds per square inch, the means for deriving this operating' oil separately from the higher-pressure propeller oil the governor head' (the pressure of which, however; may at times drop to zero) being'a featureof the'invention, and comprising an" annular metal block (Fig; 8)" 90 having bolt holes 9I' positioned to pass mounting bolts 92 (Fig. 1') on' a part of the governor" head known as'the cut outswitch and" indicated at" 93. This cut-out switch is operated: under certain conditions notfi'mportant tothe present disclosure, by change'in pressure of the engine oil which communicates'with the" switch structure through an internal passage in switch unit 93' from the'well or bore in the governorhead casting just above the" base flange I2, there being. a boss 94' cast on the'he'ad-toprovidea seat for saidcut-out switch, and" through" which boss is a bore (not seen) passing'the engine oil into said switch unit 93'.

Theannular block 50 of'Fig. 8 constitutes an adapter-which is interposed between the switch unit 93 and the'boss 94- and utilizes elongated switch mounting bolts 92 to hold the parts" in assembled relation, as in Fig. 1. The annular adaptenblock" 90, Fig. 8, isprovided' with a central' bore 95* through whichengine oil passes as aforesaid into' the cut-out switch unit 93, said block 'including'an eccentric'bo're SBcommunicating into an annular groove 91 on theswitch side of the adapterblockto receive-oil from the switch side of the" adapter; there being a third bore 98 extending from eccentric bore 96' into a larger threaded bore 90" in the side of the" block and which receives a threaded coupling nipple I on hose IN, the opposite end of which hose connects through nipple I02 (Fig. 3) with the solenoi'd valve means. The connecting hose- MI is seenin part in Fig; 1, leading from the-adapter 90 upunder the solenoid'valve'means of the control head.

As seen' in Fig; 2, the'solenoid valvemeans includes a pair of electromagnetic solenoids, I, I06, each" housed in a weatherproof casing I05a, I060; respectively (see'also Fig. 4) and" both fixed on a mounting block I01 held by bolts I08 on an integjral flange'portion I09-ofthe control-head casting:

Electrical connection terminals 1%, I050 for solenoid I05 are seen at the outer end of the latter in Fig. 6, identica1= terminals 106?), I06c being provided on solenoid I06, only terminal I061) for the latter, being visible in the views, as in Fig. 4. An outercover plate IIO, Figs. 2 and 4 held on the outer extremities of the pair of solenoids by screws III threaded into the heel slugs H2 of the solenoids- (see also Fig. 6).

seen in Figs. 1, 2 and 3, the solenoid cover plate H0 is provided with a flare I'I3 bored to communicate interiorly of the cover plate (Fig. 3'), and into" which fits one end of ashort conduct'cr' tube II'4', the opposite end of which is seated in a bore: in the block I0I' communicating into the chamber II 5 ma boss I-I5a on the governor: head casting;j' and chamber" H5 in turn communicates through a bore '6 intc'theswitch housing 10 (Fig. 3)". Thus; electrical connections(not shown)" may be passed from the switch means 8|, 82 into chamber II5'via bore II' B for engagement with certain electrical'terminal's H8 of a weatherproof connector II9 formed to provide a cover plate for the chamber H5 and having a threaded nipple portion I20 ontowhi'ch the companion coupling member (not shown) of a standard type connecting cableisthreaded. Similarly; electricalconductors'from the several solenoid'terminals I05b, I050, I061), I060 (not shown), are passed from interiorly of the solenoid cover plate IIO through tubeI I4 and-into chamber H5 for connection with certain terminals- H8, and also via bore IIB" for connection withcertain.te'rminals of" the switch means BI, 82; electrical con motions in all but the appendedcircui-t diagram. being omitted for clarity;

Each-of the solenoids has a plunger I05'd and lIlBd', respectively (Fig. 4); to the inner ends of which are secured cross bars or yokes I056 and I066, respectively, the typical construction being shown for solenoid I-05 in Fig. 6, these yokes being accommodated in cut out portions of the solenoid mountingblecli I01. Attached by screws I22 to the ends of the yoke [05c in the typical construction of Fig. 6, are the stems of upper and lower poppets I23, I24, controlling the oil flow for compressing the speeder spring. Identical'poppets I25 (Fig. i) and I25 (Fig. 5) are attached to the yoke I06e 'ofsolenoid I06, the twoyokes with corresponding solenoid plungers and" poppet; attaching screws I22 being seen-also in the vertical section of Fig. 7.

Each of'thefour poppets aforesaidis normally. seated by a spring I21 expanding between the poppet and a corresponding sealing plug I28 through which the poppet stem works, these springs also withdrawing corresponding solenoid plungers solong as the poppets remain seated;

Referring to-Fig. 7, the oil supply hose IOII is connected by nipple I02 int0=block I0? and communicates'with a bore I30 into which communicate upper-and lower bores I3I', I32 (Fig. 3 also) as in Fig. 4, upper bore I3! inturn communicates with a transverse bore I33 leading into the chamber behindupper poppet I23, there being anoutlet bore I34 (Figs. 4 and 6) into the upper chamber B-for the control piston. Thus, if solenoid core I05d be'attracted, poppet I23 will open and oil from the hose connection bore I30 (Fig. 4) will pass into bore I3I, transverse bore I33, past the unseated poppet and out through bore I34 into chamber B, thereby causing control piston 50 to be displaced downwardly with a consequent-compression of the speeder spring I8.

Oil from" lower chamber B escapes via bore: I35 (Fig. 5) around the now open poppet I24, through a vertical outlet bore I36 and thence down into the chamber 30 in the base portion of the control head casting, this exhaust oil finding its way into the drain oil chamber (not seen) of the governor.

Relaxation of the Speeder spring is effected by energizing solenoid I06, so that oil from the hose connection bore I30 (Fig. 5) is admitted through the bore I32, transverse bore I38 in behind the poppet I26, past the latter and through the outlet bore I39 into chamber B to displace the control-piston 50 upwardly, oil from upper'chamber B escaping (Fig. 4) through bore- I40 in behind poppet I25, now open, past the poppet and through exhaust bore I ll down into chamber 30 for dumping into the governor head and return in' the latter to the oil drain chamber thereof.

. Circuit connections for selective energization of the control solenoids are shown in Fig. 9, wherein there is provided a control switch I 50 on the cockpit control panel; turning this switch lever to Increase R. P. M. position causes it to close circuit with contact II, thereby completing circuit from one terminal of battery I53 via conductors I54, said switch lever and contact I50, I5I, and connecting cable conductor I55, contacts II8a of the cable connector, conductor I56, limit switch arm 82A, limit switch contact I58, to one terminal of solenoid I05, the remaining terminal of which is connected to a common return conductor I59, thence through cable coupling contacts Il8d, cable conductor I60 to battery I53, which completes the energizing circuit for solenoid I05, and will result in a downward displacement of the control piston 50 to compress the speeder spring, which in turn will decrease the propeller pitch in known manner, and thereby cause an increase in engine speed.

If cockpit control switch I50 is held closed on contact I5I as aforesaid, piston 50 will reach the limit of downward displacement, so that switch operating washer 84 (Fig. 10) atop piston rod 32 will engage limit switch operating button 83', ac tuating switch 82, and thereby causing switch arm 82A to break circuit with contact I58 and thus cutting solenoid I05 out of circuit for the time being, and further causing contact 82A to close circuit with its limit switch contact I6I, so that a circuit is now completed from battery or power source I53 through conductor I54, control switch arm I50, contact I5I, conductor I55, coupling contacts 811, conductor I56, limit switch arm 82A, limit contact I6I, conductor I62, coupling contacts II8b, conductor I63 through limit signal lamp I 64, conductor I65 back to battery or power source I53, thus lighting the limit signal lamp I64 to apprise the pilot or engineer that the propeller is set at its least pitch and no further adjustment can be made in that direction.

Similarly, if the cockpit control switch lever I50 is held closed against the Decrease R. P. M. contact I10, power is connected from battery I53, through conductor I54, control switch arm I50 closed with contact I10, cable conductor I1I, cable coupling contacts I I80, conductor I12, limit switch contact arm 8Ia. conductor I13 to, one terminal of solenoid I06, energizing the latter via return circuit I59, II8d, I60, to the remaining terminal of battery or power source I53, thus causing the control piston 50 to be displaced upwardly with a consequent relaxation of the speeder spring and increase in propeller pitch and corresponding decrease in engine speed. If the piston 50 is allowed to travel to the limit of its movement in this direction, limit switch button 83, Fig. 10, will be engaged by operating washer 84, actuating switch 6i to cause its contact arm 8Ia to break circuit with solenoid lead I13, and to close circuit with limit contact I15, thereby cutting solenoid I06 out of circuit for the time being, and energizing the limit signal means or lamp I64 via the circuit from battery I53, through control switch contacts I50, I10, as just described, returning through limit switch contacts 8Ia, I15, conductor I62, coupling contacts I I8b, cable conductor I63, lamp I64, conductor I65 returning to battery I53, thereby apprising the pilot or engineer that the limit of adjustment in this direction has been reached.

Summary of operation The complete governor control head, as illustrated in Fig. 1, is mounted on the aircraft engine close behind the propeller to be controlled, certain electrical cable connection being made with the cut-out switch unit 93, and an oil line connection being made for the propeller oil with the swivel fitting SF, all in accordance with known practices in connection with this type of governor, it being understood that the control head I I, mounted on the top flange I4 of the governor head, replaces other types of control, manual or electrical.

The adapter (Figs. 8 and 1) is interposed between the standard cut-out switch unit 93 and its mounting flange 94 on the governor head, and oil line or hose [M from this adapter is connected by nipple I02 (as in Fig. 3) to the mounting base I01 of the solenoid unit for delivery of engine oil to the flow control poppets I23, I26. The electrical control cable from the cockpit being connected or coupled with nipple I20, the device is in condition for operation, assuming the aircraft engine to be operating so that there will be pressure behind the engine oil adequate to actuate the control pistons or hydraulic means.

Referring to the circuit of Fig. 9, turning of switch arm I50 to contact I5I causes energization of solenoid I05 via circuit connections heretofore described in detail, it being assumed that the control piston is not at this time in one of its opposite limit positions, but is in some intermediate position (as in Figs. 3 and 10, the latter showing only the upper extremity of the piston rod 32) As in Fig. 6, energization of solenoid I05 a'ttracts armature plunger I05d, shifting the yoke bar [056 to the right and. withdrawing both poppets I23 and I24 from their seats against the tension of their respective seating springs I21.

Raising of said poppets I23 and I24 permits oil from the engine oil supply hose WI and solenoid base block bore I30 (Fig. '1) to pass through bores I3I, I33 (Fig. 4) in behind and thence around poppet I23 and out bore I34 into control piston chamber B, thus driving the control piston 50 downwardly and thereby tensioning the speeder spring I8, (Fig. 3), the oil in lower control chamber B at this time being expelled from said chamber through bore I35 (Fig. 5) in behind and around poppet I24, at this time open, and downwardly out bore I36 (Figs. 5 and 6) to be dumped into the space surrounding the speeder spring mechanism, from which area the expelled or exhausted oil finds its way into the governor head drain (not seen). Tensioning ,or compressing of the speeder spring as aforesaid decreases the pitch of the propeller through the agenc of high pressure oil delivered from the governor head swivel fitting SF to the propeller hub under control of the unshown pilot valve in the governor head, which is controlled in turn by the position of shaft 20. i

If the cockpit control switch arm I50 is held on contact I5I long enough to permit the control piston to reach the end of its downward travel, switch operating washer 84 (Figs. 3 and 10) willengage switch button 83 and thereby operate switch 82 to cut the solenoid I05 out of circuit and light the limit signal lamp I64 (Fig. 9).

If the cockpit control switch I50 is turned onto contact I10, solenoid I06 is energized, thereby raising poppets I25 and I26 (Figs. 4 and 5), so that oil from base block bore I30 (Figs. 7 and 5) and bores I32, I38 passes in behind and around raised poppet I26 and through bore I39 into chamber B of the control piston cylinder, thus displacing piston 50 upwardly and relaxing the speeder spring :13 (Fig. 3),, oil 'from the upper chamberB'being expelled through bore Mfl be- Ihindandaround open-poppet I25 and out bore 'l4'l '(Fig. 4) tom dumped "into thespace about thespeeder spring assemblyto return ;to the'gov- .ern'orheadoil drain. a

If thecontrol piston is permitted to, reach the end of -its upward "travel, as aforesaid, switch operating washer "8.4 will rise into engagement with limit switch operating button 83 (Figs. .3 and '10) "and, actuatethe upper'limit switch 81 to cut solenoid I06 outof .circuit and to light the limit. signal? lamp '1 64 '(Fig. 19) :in. accordance :with

detailed gcircult connections heretofore described.

'During the aforesaid upward and downward displacements of the controlpistonifl, regulating piston 60 moves correspondingly and displaces a captive speed controlling or regulating fluid, contained'in chambersAand A1, from photo the other ,of said chambers through. orifice 66, there- "by regulating the speed of said displacementof .gcontrol piston 50, theregulated speed being.selectivelydetermined by the sizeof orifice 66 and the viscosity of the captive speed controlling fiuid, said viscosity also being selected for an optimum .flow rate under opposite extremes of tempera- 'ture, .said viscosity in general'being quite low.

jIt is important to observe that the disclosed structure, embodying as "it does twin control valves for each direction of displacement of the unitary ,coritrol piston, .makes possible a locking of Lthesaidpiston in whatever position it is set,

since the fluid displacement in the opposite chambers B and B is at all :times proportionately inverse, .and ,piston '50 cannot move under extraneouseinfiuence,sojlong as the vpoppets remain sea-ted, but is in effect hydraulically locked in position.

The stated andiriherent advantages and ob-' ,jectsof the invention may be realized in modi- ..iiedlformso'f thespecific iorm of the device set .Iforthiin detail herein for purposes of disclosure to .thepublic .in Letters Patent,,and nolimitations .are thereby intended excepting as may be expresslyprovided.bythe appended claims.-

.Irclaim:

1. Hydraulic control means ,for use with aircraft propeller-pitchgovernors of the type having a speeder spring, said means comprising: a control head ..adapted..to be mounted on a said governor vandincluding acylind-er and a control ,piston .reciprocable therein, speeder-spring .en-

gaging meansmovedbysaid pistonin its opposite motions and projecting for engagement with a .speeder. spring when the'controLhead is mounted on the governor head forcompressing and relax- :ing saidlspeeder spring, a first set of poppets yieldingly seated and one eachof thesamecommunicating to a different side of said control piston, means directing hydraulic displacement .for admission of fluid to said cylinder to move :10 pet of the second set, when open, permitting escapeof-fluid'from the'side of the control :piston opposite that "to which said displacement fluid is admitted by said first poppet of said second set; 'means carried on "said 'head and operable for opening either set of 'poppets at will; means directing hydraulic ,displacement'fiuid to the first poppet of *the second set, =said fluid normally retained on opposite sides of the control piston when said poppets are all closed and seated, whereby said control piston is hydraulically locked in position to maintain said speederspring engagingmeansin a desired condition of 'compression-or relaxation.

'2. For use with an aircraftgovernor head of the'type'includinga connectionwith a source-of engine oilunder pressure'and acut-out switch device in operative communication 'with said source, improvements oomprisingto wit: a controlhead adaptedto be mounted on said governor head, hydraulic means 'in 'said control head for actuating "a controlled instrumentality in said governor head, said hydraulic means operated by 'sai'd en-gin'e oil,-valve means controlling 'fiow of 'said engine on relative .to said hydraulic means, 'and:means'for deriving engine .oilfrom the governor'headffor operation of thehydraul'ic means as aforesaid, said last-mentioned means including an'adapter arranged and constructed to 'be interposed between said ,cut-out switch-device andsaid engine oilsource and leading off engineoil ;to said valve means.

3. Hydraulic control apparatus comprisingtwo pistons on a common rod and working in .a common cylinder sealed at both ends with a "sealing-plate between said pistons and affording, hydraulic chambers on opposite sides of both pistons, an outer :said piston constituting a regualtingpiston having a fluid escape orifice therethrough, asecond outer .one of 'saidpistons constituting a working piston, av captive regulating fiuidgin the "flanking chambers of said regulating piston, an'inlet duct in said cylinder communicating with each 'side of said working piston,

an outlet duct in said cylinder communicating with each side of said working piston, ,PODpets regulating'fluidiflow in said ducts, and control means including mechanism normallyclosing all said DODpets and actingto move said poppets selectively in pairs each consisting "of one inlet duct on a given side of the'working piston and one outlet-duct on the correspondingly opposite side of said working piston, .whereby the latter ma be'reversely displaced at a regulatedrate by selective opening of either pair of .said poppets and hydraulically locked in any position by normal closure of all said poppets .as aforesaid.

4. Hydraulic control apparatus for use with an aircraft propeller governor including a speeder spring, said apparatus comprising: a single cyl- .inder head adapted to be mounted on said governor opposite said speeder spring, a pair of coreciprocable pistons in said cylinder and means reciprocable thereby and adapted to be operatively interconnected with said speeder spring'for .tensioning and relaxing the latter responsive to opposite movements of said pistons, two sets of solenoid-operated dual valve means mounted on said head for controlling flow of hydraulic displacement fluid selectively to and from opposite sides of one of said pistons constituting the control piston to effect selective reciprocationthereoflsaid other piston working against a captive {fluid in said cylinder sealed off from said first :piston,

orifice means in said second piston permitting regulated escape of said captive fluid past said second piston in opposite movements thereof to regulate the displacement speed of said pistons under controlled hydraulic flow as aforesaid, said valve means being normally closed to trap said displacement fluid on both sides of said control piston to lock the latter in all positions, and means providing a stationary insert seal in said cylinder segregating said captive fluid from said control piston.

- 5. Apparatus of the class described comprising a closed cylinder, two pistons working in said cylinder on a common rod but separated by an insert sealing plate and all jointly dividing said cylinder into four chambers, one of said pistons having an escape orifice for passage of speed-regulating fluid from one to another side thereof, cylinder ducts in pairs each pair interconnecting respectively opposite sides of a second one of said pistons, a pair of poppets for each said pair of ducts, and means for simultaneously opening one, and closing one of the poppets of each said pair, whereby to admit a fluid-pressure medium selectively to either side of said second piston for efiecting reverse displacements thereof, and means for connecting a source of fluid-pressure medium to said pairs of poppets, together with cylinder duct means connecting with said pairs of ducts for dumping expelled fluid-pressure medium from the chambers on opposite side of said second piston to the exterior of said cylinder through any of said poppets which are opened as aforesaid.

6. A fluid-operated servomotor comprising two pistons on a common drive rod and working in a single closed cylinder having a removable insert-sealing plate between said pistons and cooperable with the latter to define four chambers, a pair of ducts connecting opposite sides of an outer one of said pistons, constituting a working piston, through a first. pair of spring-seated poppets to a fluid pressure line and an exhaust port, respectively, a second pair of ducts respectively connecting opposite sides of said working piston in a reverse sense from the first said pair with said line and an exhaust port through a second pair of spring-seated poppets, a trapped speedregulating fluid in the chambers flanking another outer one of said pistons, said last piston having an escape orifice therethrough, and means for selectively seating and unseating either pair of said poppets to effect reverse displacements of said working piston and to hold said piston. in any displaced position in normally seated condition of the poppets.

'7. A fluid-operated servomotor comprising a closed cylinder, a pair of pistons spaced apart on a common drive rod therein, fluid supply inlet ducts connecting to opposite sides of a working one of said pistons, a separate poppet closing the supply duct to each said side, a cylinder exhaust duct for efliuent fluid from each said side, a separate poppet closing each said exhaust duct, mechanism for simultaneously opening and closing said poppets in pairs each pair consisting of one poppet for said supply duct and one poppet for said exhaust duct, whereby said working piston may be reversely displaced and be hydraulically locked in position by fluid trapped on opposite sides of said working piston as a result of closure of all said poppets.

' 8. A fluid-operated servomotor comprising a head having a base constituting a cylinder closed at one end of the head and opening through into a base :avity in opposite end of the head, a fluid seal between said cylinder and cavity, a piston rod working in said cylinder through said seal and piston means consisting of two pistons spaced apart on said rod in said cylinder, one piston havingfiuid escape passage therepast, a speed-regulating fluid transferred from one to another side of said one piston responsive to reciprocation thereof, two sets of fluid inlet and exhaust ducts the ducts of each set communicating from a fluid supply connection in said head in relatively reverse relation to opposite working sides of the remaining piston, twin sets of linked poppets for each said set of ducts, and solenoid means carried on said head and selectively actuating said poppet sets to unseat the latter, from a normally seated condition, in pairs each consisting of one inlet and one exhaust poppet whereby to displace said piston assembly selectively in reverse directions by fluid from said supply, said exhaust ducts dumping into said cavity, and said piston communicating into said cavity for operative connection with a load. V

9. A servo-motor for attachment as a control head on a governor head, and comprising, to wit: a body including a cylinder adapted for mounting on agovernor head; two spaced pistons working on a common rod in said cylinder, the latter being closed at both ends and having an intermediate sealing portion between said pistons whereby said cylinder is divided into four chambers one of which is situated on a side of each piston such that each piston is flanked by a sealed chamber, a speed-regulating orifice by-passing a first one of said pistons to interconnect the flanking chambers therefor, a speed-regulating fluid trapped on said flanking chambers, a main intake for fluid under pressure to a body portion of said cylinder, an inlet duct in said body leading from said intake into said cylinder to each side of the second and working one of said pistons, an exhaust duct in said body leading from each side of said working piston to discharge into said governor head, poppets normally seated to close all of said ducts, a pair of solenoids carried on said body and each energizable to selectively open a pair of said poppets, each said pair consisting of one inlet and one exhaust poppet for the corresponding ducts, such that energization of either solenoid will admit said fluid under pressure to one or the other side of said working piston to displace the latter oppositely under control of said regulating fluid, said piston rod being adapted for connection with governor means actuated thereby in said governor head.

10. The construction set forth in claim 9 fur.- ther characterized by the addition of a switch chamber on said cylinder in alignment with the axis of said piston rod, a limit switch in said switch chamber and including actuating means engaged by means on said piston rod in a certain position'of displacement for control of a limit signaling circuit, and means on said body affording circuit connections with said solenoids and said limit switch.

EDWARD J. COLLINS.

REFERENCES CITED Thefollowing references, are of record in file of this patent:

UNITED STATES PATENTS Name Date Thompson Sept. 1 1 908 (Other references on following page) Number UNITED STATES PATENTS Name Date Scott July 27, 1915 I Farmer Oct. 15, 1918 Lang May 2, 1922 Lamb Oct. 9, 1923 Ricardo Jan. 27, 1931 Charlton Jan. 5, 1932 Number Number Name Date Martin Jan. 17, 1939 MacNeil et a1. Oct. 20, 1942 Martin Oct. 26, 1943 FOREIGN PATENTS Country Date Great Britain Dec. 11, 1939 France Apr. 4, 1933 

